Transducer



F. V. HUNT TRANSDUCER May 6, 1952 Filed April 5, 1946 swam 1M FREDERICKV. U NT I ate'nted May 3, 1952 "UNITED STATES PATENT OFFICE TRANSDUCERFrederick V. Hunt, Belmont, Mass, assig'nor to the United States ofAmerica as represented by the Secretary of the Navy Application April 5,1946, Serial No. 659,714

(01. lib-209) 4 Claims. 1

The present invention relates in general to transducers and isparticularly concerned with improvements in transducers of the radiallyexpanding magnetostrictive type for use in underwater soundapplications.

It has heretofore been proposed to construct radially expandingtransducers with laminated cores effected by stacking a plurality ofannular stampings of magnetos'trictive material over which a toroidalwinding is placed. Such constructiori has proved expensive and wasteful,since the annular rings are stamped or punched from sheet metal stock,thus resulting in an extremely high percentage of metal Waste.

It has been found that transducers having laminated cores constructed inthe above manner have a resonance curve which is relatively sharp, sothat the transducer is limited to use over a relatively narrow frequencyband. Reduction in the wall thickness of the laminated core will resultin spreading out of the usable frequency band, and although somesacrifice in efhciency is made by reducing the wall thickness, this iscompensated for in the increase of effective band width. In thepresently formed annular rings, decrease of the width of the wallforming portions will introduce manufacturing difiiculties.

The present invention proposes to overcome the limitations in presentconstructions by winding a ribbon of magnetostrictive material, such asnickel, edgewise around a mandrel to form, in eifect, a laminatedcylindrical core having a wall thickness equal to the edge width of theribbon. The turns of the wound ribbon are insulated and secured togetherto form a substantially unitary core structure.

Having the foregoing in mind, it is a primary object of the hereindescribed invention to providean improved core structure which is coo-'-nomical to construct and which results in a sav ing of material, andyetwhich has a relatively flat response over a wide range offrequencies.

Another object is to provide an improved magnetostrictive transducerhaving a core possessing the advantages inherent in a laminatedstructure, but which can be fabricated from a thin ribbon material, andthus effectively utilize all the material.

A further object is to provide an improved method for the fabrication ofa cylindrical core of magnetizable material, which is susceptible of usein producing the core as a separate article of manufacture.

Still other objects and advantages of my invention will be apparent fromthe specification.

'rhe'features of novelty which I believe to be characteristic of myinvention are set forth with particularity in the appended claims. Myinvention itself, however, both as to its fundamental principles and asto its particular embodiments, will best be understood by reference tothe specification and accompanying drawings, in which:

Figure 1 is a perspective view of a transducer element embodying thefeatures of the present invention;

Figure 2 is a view schematically representing a modified formofconstruction;

Figure 3 is a View diagrammatically representing the steps of myimproved method for corn structing the core of the transducer; and

Figure 4 is a fragmentary view of an enlarged section of the corestructure, showing the interrelation of the core elements.

Referring now to the drawings, there is shewn in Figure 1-, a radiallyexpanding laminated core type transducer which embodies the features (ifthe present invention. The disclosed construction comprises a toroidalwinding it placed on a cylindrical thin walled core H as schematicallyrepresented in Figure 2.

It is thought that the construction of the core will best be understoodfrom the following description of one method I utilize for its fabrica=tion.

A ribbon l2 of magnetostrictive material, such as nickel, of desirededge width is wound edgewise around a mandrel I3, as shown in Figure-3.The ribbon is laid in the form of a helix, the turns of which aremaintained in close relationship between an abutment surface l4 carriedby an end member l5 and a movable collar member [6 which is springpressed by an expansion spring ll against the ribbon as it is beingwound on the mandrel. v

It will be apparent in Fig. 2 that the wall thickness of the core IIwill depend upon the edge width of the ribbon used. In practice, I havefound that edge widths of E,- and A; inch are well suited for thispurpose. In winding a core from a thin ribbon as described, it has beenfound desirable to anneal the ribbon prior to winding it on the mandrelin order to increase its ductility. As shown in Figure 3, the initialannealing is represented by the application of a flame as from a Bunsenburner [8, although it will be appreciated that any other suitableheating device may be utilized. Moreover, it is also preferable tore-anneal the ribbon after it is wound on the mandrel in order torelieve it of any stresses which may have been set up therein during thewinding. This may be accomplished in any appropriate manner and, forpurposes of illustration I have disclosed a heating element l9 withinthe mandrel, this element being connected to an appropriate electricsupply source represented by conductors 20 and 2|. A switch 22 is shownfor cont olling the heating element.

In order to consolidate the wound ribbon so as to form a core unit ofstable construction, I have found it desirable to utilize a suitableconsolidation material for insulating the turns relative to each otherand bonding them together. Various compounds may be utilized for thispurpose, such as resins, synthetic rubbers and the like. One suchcompound which has worked very satisfactorily is a material which iscommonly utilized to bond rubber to metal, this material beingcommercially known as Cycleweld."

The consolidation material may be applied between the turns, while thewound core member is still on the mandrel. It is only necessary torelease the pressure of the spring H, which will permit movement of thecollar l6 away from the end of member l and a spreading apart of thecoil turns sufiiciently to introduce the consolidation materialtherebetween. A preferable manner of applying the consolidationmaterial, however, is to spray it onto the ribbon surface as from anozzle 23, as diagrammatically illustrated, just prior to its being laidedgewise on the mandrel. If the consolidation material is of suchcomposition as to require the application of heat to bond and form aninsulation between the turns of the coiled ribbon, this heat may beapplied by the heating element I9 within the man drel, as required.

As shown in detail in Figure 4, a cylindrical core structure preparedaccording to my method will efiect alternate convolutions 24 with theinsulating and binding material as shown at 25 respectively disposedbetween the convolutions and binding them together into a stable coreunit.

When the transducer element is to be operated at magnetic remanence, acontinuous toroidal winding, as shown in Figure 1, is utilized. Where itis desired to polarize the transducer element, a polarizing magnet 26may be placed loosely inside the core prior to placing the coil windingthereon, as shown in Figure 2. The magnet 28 extends diametricallyacross the core cylinder. In such case, the winding is separated intosections as indicated at Illa and Hlb and wound in opposite directionfor producing relatively opposed polarities in the core.

The improved method of my invention permits the utilization of narrowwidth ribbons and the fabrication of a thin laminated core member havinga broad frequency band; large savings in the metal constituting the coreelement; and the manufacture. of a core element as a separate article ofmanufacture susceptible of general use.

I claim:

1. A magnetostrictive transducer comprising a winding, and a hollowcylindrical core formed of a ribbon of magnetostrictive material woundedgewise in a helix, said ribbon having a thin edge Width, said corehaving a wall thickness approximately equal to the edge width of saidribbon, whereby the said transducer has a rela-- tively flat responseover a wide frequency range.

2. A magnetostrictive transducer comprising a winding, and a hollowcylindrical core structure formed of a helically wound ribbon ofmagnetostrictive material having its turns insulated and bonded relativeto each other, said ribbon having a thin edge width, said core having awall thickness approximately equal to the edge width of said ribbon,whereby the said transducer has a relatively flat response over a widefrequency range.

3. A magnetostrictive transducer comprising a hollow cylindrical coreformed of a helically wound ribbon of magnetostrictive material, apolarizing magnet disposed diametrically within the core, and a toroidalwinding on said core, said winding having sections for relativelymagnetizing said core in opposed directions, said cores having a wallthickness approximately equaly to the width of said ribbon. 4. As anarticle of manufacture, a magnetizable hollow cylindrical core structureincluding a cylinder formed of windings comprising a helically woundribbon of magnetizable material laid edgewise, and means bonding andinsulating the ribbon windings, said ribbon having a thin edge width,said core having a wall thickness approximately equal to the edge widthof said ribbon, whereby said core structure is adapted for use in atransducer having a relatively flat response over a wide frequencyrange.

FREDERICK V. HUNT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Gauthier Mar. 4, 1947

